Load span tag axle system

ABSTRACT

Systems and apparatuses include a tag axle system including an axle assembly, a linkage coupling the axle assembly to a vehicle chassis, and a hydraulic cylinder coupled between the vehicle chassis and the axle assembly. The hydraulic cylinder actuates the axle assembly between a raised position and a lowered position, and acts as a spring damper suspension component.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/295,512, filed on Mar. 7, 2019, and claims the benefit of U.S.Provisional Patent Application No. 62/640,393, filed on Mar. 8, 2018,and U.S. Provisional Patent Application No. 62/682,529, filed on Jun. 8,2018 all of which are incorporated by reference in their entireties.

BACKGROUND

Work vehicles are known to carry heavy loads, and often to carry theseloads over unpaved surfaces such as dirt roads and around constructionsites. In particular, concrete trucks carry large drums full of concretelong distances and often must traverse unpaved surfaces to access thesite for unloading the concrete from the drum. Concrete trucks typicallyinclude a cab for the operator and a rotatable drum behind the cab forcontaining and mixing concrete. Such concrete trucks further typicallyinclude a set of front wheels for steering, and plural rear drive axlescarrying dual wheel or wide single line arrangements mounted on acontinuous elongate chassis for load-support. For additionalload-support, particularly in-transit when the drum is substantiallyfull, a concrete truck can benefit by having a pivotally mounted tagaxle (auxiliary axle) system able to operate between a raised position,in which it is carried by the truck, and a lowered/deployed position inwhich the tag axle and its wheels share the truck's load. Not only doesthe tag axle system assist in balancing the load carried by the concretetruck when the drum is fully loaded, it may facilitate the concretetruck carrying a higher total payload than would otherwise be permitted,because weight restrictions placed on vehicles traveling over highwaysare typically measured in terms of load per axle in combination withoverall spacing between axles of a vehicle. By deploying a tag axlesystem, the number of axles as well as the spacing thereof can beincreased when the truck is heavily loaded, thereby enabling the truckto transport a higher total legal payload.

SUMMARY

One exemplary embodiment relates to a tag axle system that includes anaxle assembly, a linkage coupling the axle assembly to a vehiclechassis, and a hydraulic cylinder coupled between the vehicle chassisand the axle assembly. The hydraulic cylinder actuates the axle assemblybetween a raised position and a lowered position, and acts as a springdamper suspension component.

Another exemplary embodiment relates to a tag axle system that includesan axle assembly including an axle beam that includes a plurality ofplates welded together, each plate defining no more than two bends, anda plurality of axle brackets fastened to the axle beam. The tag aclesystem also includes a hydraulic cylinder coupled between a vehiclechassis and the axle assembly. The hydraulic cylinder actuating the axleassembly between a raised position and a lowered position, and acting asa spring damper suspension component.

Another exemplary embodiment relates to tag axle system that includes anaxle beam including a plurality of plates welded together, each platedefining no more than two bends, a hydraulic cylinder coupled between avehicle chassis and the axle beam, and a kingpin. The hydraulic cylinderactuates the axle beam between a raised position and a lowered position,and acts as a spring damper suspension component. The kingpin is coupledto the axle beam and arranged at a kingpin caster angle that ismaintained in all loading conditions when the axle assembly is in thelowered position.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited herein.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a top, front, left perspective view of a load span tag axle(LSTA) system in a raised position, with the wheels removed, accordingto an exemplary embodiment,

FIG. 2 is a top view of the LSTA system of FIG. 1 in the raisedposition,

FIG. 3 is a top, front, right perspective view of an axle beam accordingto an exemplary embodiment.

FIG. 4 is a top, rear, right perspective view of the axle beam of FIG.3,

FIG. 5 is a section view of the axle beam of FIG. 3, showing a partialcross-section through the left brackets.

FIG. 6 is a bottom, rear, right perspective view of the axle beam ofFIG. 3 with part of the axle beam removed.

FIG. 7 is a schematic diagram of a hydraulic system of the LSTA systemof FIG. 1,

FIG. 8 is a left side view of the LSTA system of FIG. 1 in the raisedposition,

FIG. 9 is a rear view of the LSTA system of FIG. 1 in the raisedposition,

FIG. 10 is a top, front, left perspective view of the LSTA system ofFIG. 1 in a lowered position,

FIG. 11 is a top view of the LSTA system of FIG. 1 in the loweredposition,

FIG. 12 is a left side view of the LSTA system of FIG. 1 in the loweredposition,

FIG. 13 is a rear view of the LSTA system of FIG. 1 in the loweredposition.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to the figures generally, the various exemplary embodimentsdisclosed herein relate to systems, apparatuses, and methods for a tagaxle of a vehicle including a four-bar swing linkage mounted between anaxle assembly and a vehicle chassis that provides a controlled motion ofthe tag axle between a raised position and a lowered position. The axleassembly includes an axle beam developed for ease-of-manufacturing. Twodual action hydraulic cylinders (i.e., dual acting hydraulic cylinders)are coupled between the axle assembly and the vehicle chassis and servetwo primary purposes. First, the dual action cylinders drive theactuation of the four-bar swing linkage between the raised position andthe lowered position. Second, the dual action cylinders are part of theprimary suspension for the tag axle. Each dual action cylinder is incommunication with or includes an accumulator with a gas chamberproviding a spring and/or damper action. Additionally, the tag axleincludes a connecting rod that links a steering knuckle of each of twowheel assemblies. The wheel assemblies also include steering centeringsprings that act to bias the tag axle toward a centered steeringposition. The four-bar swing linkage is arranged around the connectingrod and sized so that a kingpin caster angle of each of the wheelassemblies remains constant or nearly constant as the tag axle movesbetween the raised position and the lowered position.

In one exemplary embodiment, and as shown in FIGS. 1 and 2, a vehiclechassis 20 of a vehicle is structured to support the vehicle for travel.In some embodiments, the vehicle is a concrete truck including wheelassemblies, a cab, and a concrete mixing cylinder supported on orcoupled to the vehicle chassis 20. In some embodiments, the portion ofthe vehicle chassis 20 shown in FIGS. 1 and 2 is a rearward portion ofthe vehicle chassis 20. In some embodiments, the vehicle chassis 20 isshaped differently but still provides a rigid structure.

A load span tag axle (LSTA) system 24 is coupled to the vehicle chassis20 and includes a chassis mount 28 that is rigidly attached to thevehicle chassis 20, and an axle assembly 32 that supports two hubs 36(each hub 36 configured to support a wheel) and is connected to thechassis mount 28 by a four-bar swing linkage that includes a right upperlink 40, a left upper link 44, a right lower link 48, and a left lowerlink 52. A right hydraulic cylinder 56 and a left hydraulic cylinder 60are connected between the chassis mount 28 and the axle assembly 32 and,in one mode of operation, actuate the axle assembly 32 between a raisedposition (shown in FIG. 1) and a lowered position (shown in FIG. 10). Ahydraulic system 64 controls operation of the right hydraulic cylinder56 and the left hydraulic cylinder 60. In other embodiments, the LSTAsystem 24 includes another type of actuator in addition to or in placeof the right hydraulic cylinder 56 and the left hydraulic cylinder 60(e.g., a rotary hydraulic actuator, another type of rotary actuator,another type of linear actuator, etc.).

The chassis mount 28 is attached to the vehicle chassis 20 (e.g., withfasteners, etc.). In some embodiments, the chassis mount 28 is welded tothe vehicle chassis 20 or formed as a part of the vehicle chassis 20.The chassis mount 28 includes a right upper mount bracket 68, a rightlower mount bracket 72, a left upper mount bracket 76, and a left lowermount bracket 80. The right upper mount bracket 68 is structured to beconnected to the right upper link 40, the right lower mount bracket 72is structured to be connected to the right lower link 48, the left uppermount bracket 76 is structured to be connected to the left upper link44, and the left lower mount bracket 80 is structured to be connected tothe left lower link 52. In some embodiments, the links 40, 44, 48, 52are connected to the mount brackets 68, 72, 76, 80 with capturedbearings and fastener arrangements. In some embodiments, the links 40,44, 48, 52 are permitted to move relative to the mount brackets 68, 72,76, 80 with one degree of freedom (e.g., rotation) and are substantiallyconstrained from moving in a side to side direction.

The chassis mount 28 further includes a right actuator mount bracket 84that is structured to be connected to the right hydraulic cylinder 56and a left actuator mount bracket 88 that is structured to be connectedto the left hydraulic cylinder 60. Similar to the mount brackets 68, 72,76, 80, the actuator mount brackets 84, 88 can be connected to thehydraulic cylinders 56, 60 with captured bearings and fasteners topermit rotation of the hydraulic cylinders 56, 60 relative to thechassis mount 28 while inhibiting other movement of the hydrauliccylinders 56, 60.

The axle assembly 32 includes an axle beam 92 that includes a rightupper axle bracket 96 structured to be connected to the right upper link40, a right lower axle bracket 100 structured to be connected to theright lower link 48, a left upper axle bracket 104 structured to beconnected to the left upper link 44, and a left lower axle bracket 108structured to be connected to the left lower link 52. Similar to themount brackets 68, 72, 76, 80, the axle brackets 96, 100, 104, 108 canbe connected to the links 40, 44, 48, 52 with captured bearings andfasteners to permit rotation of the links 40, 44, 48, 52 relative to theaxle beam 92 while inhibiting other movement of the links 40, 44, 48,52. The axle beam 92 also includes a right actuator axle bracket 112that is structured to be connected to the right hydraulic cylinder 56,and a left actuator axle bracket 116 that is structured to be connectedto the left hydraulic cylinder 60. The actuator axle brackets 112, 116can be connected to the hydraulic cylinders 56, 60 with capturedbearings and fasteners to permit rotation of the hydraulic cylinders 56,60 relative to the axle beam 92 while inhibiting other movement of thehydraulic cylinders 56, 60. In the embodiment of FIGS. 1-2, each of thelinks 40, 44, 48, 52 is secured to the axle beam 92 using a bolt (notshown) that extends through holes in the axle brackets 96, 100, 104, 108and a bushing at one end of the link 40, 44, 48, 52.

According to the exemplary embodiment shown in FIGS. 3-6, the axle beam92 is formed from ten metal plates, shown as forward plate 214 (FIG. 3),upper end plates 216, lower end plates 218, upper midplate 220, lowermidplate 222, and rear plate 224, and end rear plates 226 that arewelded together. In various alternative embodiments, the number andarrangement of plates may differ. Each of the plates 214, 216, 218, 220,222, 224, 226 is made from a single piece of sheet metal (e.g., carbonsteel) that is bent into the desired shape. As shown in FIGS. 3-6, eachof the plates 214, 216, 218, 220, 222, 224, 226 includes no more thantwo bends, an apparatus configuration that simplifies manufacturing ofthe axle beam 92 and provides complete access to inner and outersurfaces of each plate 214, 216, 218, 220, 222, 224, 226 prior towelding.

As shown in FIG. 6, each of the axle brackets 96, 100, 104, 108 isaffixed to the forward plate 214 using a plurality of fasteners 232(e.g., lockbolts such as Huck lockbolts, although any other suitablefastener may be used) that extend through a connection hole the axlebracket 96, 100, 104, 108 and a corresponding mounting hole in theforward plate 214. The two-bend plate assembly provides user access toan inside surface 228 of the forward plate 214, which is required inorder to secure each one of the plurality of fasteners 232 intoposition. Among other benefits, using a plurality of fasteners 232 tosecure the brackets to the forward plate 214 eliminates the risk of weldfatigue at critical attachment points. A coupling 230 (FIGS. 3-5) forthe kingpin 136 (see also FIGS. 1-2) is disposed at both ends of theaxle beam 92. Each coupling 230 is welded to at least one of the forwardplate 214, upper end plate 216, lower end plate 218, and end rear plate226.

The axle assembly 32 also includes a right wheel assembly 120 and a leftwheel assembly 124. The left wheel assembly 124 is substantially similarto the right wheel assembly 120, with like numerals identifying likecomponents (i.e. components for the left wheel assembly 124 that aresimilar to the right wheel assembly 120 are denoted using like numbersin prime series). The right wheel assembly 120 is mounted to the axlebeam 92 and includes a spindle/knuckle 128, a brake assembly 132, akingpin 136 coupled between the spindle/knuckle 128 and the axle beam 92at a kingpin caster angle to allow rotation of the wheel assembly 120relative to the axle beam 92 thereabout, and a steering arm 140extending from the spindle/knuckle 128 toward the vehicle chassis 20.The hub 36 is attached to the spindle/knuckle 128 and is free to rotatethereabout. The brake assembly 132 is structured to slow the rotation ofthe hub 36 via frictional engagement. In some embodiments, the brakeassembly 132 is a drum brake assembly, a disk brake assembly, a manuallyoperated brake system, and electronically operated brake system, ahydraulic brake system, or another brake system, as desired.

The axle assembly 32 further includes a steering assembly having aconnecting rod 144 connected between the steering arms 140, 140′, and acentering system having a right spring damper 148 connected between theaxle beam 92 and the right steering arm 140 and a left spring damper148′ connected between the axle beam 92 and the left steering arm 140′.The connecting rod 144 ties the right wheel assembly 120 to the leftwheel assembly 124 so that rotation of the wheel assemblies 120, 124 iscoordinated. In other words, the right wheel assembly 120 is inhibitedfrom rotating relative to the left wheel assembly 124. The right springdamper 148 and the left spring damper 148′ act to bias the wheelassemblies 120, 124 toward a center position (e.g., a position thatdrives straight). The connecting rod 144 is arranged vertically betweenthe upper links 40, 44 and the lower links 48, 52 and in front of theaxle beam 92. Additionally, the caster angle of the wheel assemblies120, 124 can be changed to move the steering axis in forward orbackward, as desired.

Returning to FIG. 2, the four-bar swing linkage that couples the chassismount 28 to the axle assembly 32 includes the right upper link 40, theleft upper link 44, the right lower link 48, and the left lower link 52.The vehicle chassis 20 defines a central axis A extending longitudinally(e.g., front to back). The upper links 40, 44 are angled laterallyoutward (e.g., away from the central axis A) as they extend toward theaxle beam 92. As shown in FIG. 2, each of the upper links 40, 44 definean upper link angle B relative to the central axis A. The upper linkangle of the right upper link 40 is mirrored relative to the upper linkangle of the left upper link 44. In some embodiments, the upper linkangle B is about nine degrees (9°). In some embodiments, the upper linkangle B is between about five degrees (5°) and about fifteen degrees(15°). The lower links 48, 52 are angled laterally inward (e.g., towardthe central axis A) as they extend toward the axle beam 92. As shown inFIG. 2, each of the lower links 48, 52 define a lower link angle Crelative to the central axis A. The lower link angle of the right lowerlink 48 is mirrored relative to the lower link angle of the left lowerlink 52. In some embodiments, the lower link angle C is about ninedegrees (9°). In some embodiments, the lower link angle C is betweenabout five degrees (5°) and about fifteen degrees (15°). In someembodiments, the upper link angle B and the lower link angle C aredifferent. Additionally, the upper link angle B and the lower link angleC are mirrored relative to each other so that there isone-hundred-sixty-two degrees (162°) between the upper link angle B andthe lower link angle C). The upper link angle B and the lower link angleC provide support in case of side loading from wheel scrubbing or otherforces acting in a side-to-side direction. In another embodiment, thefour-bar swing linkage has links that are otherwise positioned. By wayof example, the upper links 40, 44 may angle laterally inward and thelower links 48, 52 may angle laterally outward.

As shown in FIGS. 8 and 12, each of the right upper link 40, the leftupper link 44, the right lower link 48, and the left lower link 52include a bend 230 between a midpoint of the links 40, 44, 48, 52 andthe axle beam 92 (the bend 230 proximate to the end of each link that isconnected to the axle beam 92). The bend 230 in each link 40, 44, 48, 52increases the space contained between the upper links 40, 44 and thelower links 48, 52 as compared to a design configuration that uses linkshaving a straight shaft.

The four-bar swing linkage including the right upper link 40, the leftupper link 44, the right lower link 48, and the left lower link 52 isarranged as a parallelogram linkage (i.e., a parallelogram arrangement)and is arranged to maintain the kingpin caster angle regardless ofloading in the lowered position. The kingpin caster angle affects wheelchatter and wear characteristics. Controlling the kingpin caster anglethroughout use in the lowered position provides an improvement overprior tag axles where the kingpin caster angle can change or become toolow in some loading conditions. Some prior tag axles used shims in anattempt to control the kingpin caster angle, but were unable to addressall loading conditions. The parallelogram linkage substantiallyeliminates the use of shims and addresses more loading conditions.

In some embodiments, the four-bar linkage is not arranged as aparallelogram linkage. A non-parallelogram arrangement may result insmall changes to the kingpin caster angle but the variance of thekingpin caster angle may be maintained within an acceptable range whenin the lowered position. While the kingpin caster angle may be variable,the non-parallelogram linkage may provide additional space between thelinks as they actuate between the raised position and the loweredposition. Additionally, the non-parallelogram linkage may provide agreater axle lift height. The additional space is created by the axlerotating forward (more upright) as it lifts which increases the verticalspacing between the attachment points on the axle.

As shown in FIG. 7, the right hydraulic cylinder 56 includes a cylinder156 structured to couple with the right actuator mount bracket 84, aplunger 160 dividing the cylinder into a first chamber 164 and a secondchamber 168 that is isolated from the first chamber 164, and a rod 172extending from the plunger 160 and structured to couple with the rightactuator axle bracket 112. The left hydraulic cylinder 60 issubstantially similar to the right hydraulic cylinder 56 and includes acylinder 156′ structured to couple with the left actuator mount bracket88, a plunger 160′ dividing the cylinder into a first chamber 164′ and asecond chamber 168′ that is isolated from the first chamber 164′, and arod 172′ extending from the plunger 160′ and structured to couple withthe left actuator axle bracket 116. The right hydraulic cylinder 56 andthe left hydraulic cylinder 60 are dual action hydraulic cylinders thatcan be actively driven between a retracted position corresponding to theraised position of the LSTA system 24 and an extended positioncorresponding to the lowered position of the LSTA system 24.

With continued reference to FIG. 7, the hydraulic system 64 includes avehicle hydraulic system 176 that controls various systems and subsystemof the vehicle. In some embodiments, the vehicle hydraulic system 176operates the concrete mixer, a vehicle suspension system, a vehicletransmission, and/or other vehicle systems. A pump 180 is arranged incommunication with the vehicle hydraulic system 176 and operable toprovide high pressure hydraulic fluid to a control valve 184. In someconstructions, the control valve 184 is a two-position four-way spoolvalve that includes a return spring 188 and a solenoid 192. In someconstructions, the control valve 184 may include a double acting inchingcircuit, or another control architecture, as desired. A controller 196is arranged in communication with the vehicle hydraulic system 176, thepump 180, and the control valve 184 to control operation of the LSTAsystem 24 between the raised position (e.g., a lift mode) and thelowered position (e.g., a suspension/operational mode).

The hydraulic system 64 also includes an accumulator 200. In oneembodiment, the accumulator 200 includes a movable element, shown as apiston 204. The movable element (e.g., the piston 204, a diaphragm,etc.) separates a spring chamber 208 from a collecting chamber 212 thatis in fluid communication with the first chamber 164 of the righthydraulic cylinder 56 and the first chamber 164′ of the left hydrauliccylinder 60. In some embodiments, the spring chamber 208 is charged withnitrogen or another gas to a predetermined pressure calibrated to adesired spring rate. In some embodiments, the spring chamber 208 is incommunication with a pressure source (e.g., a pneumatic compressor) andmaintained at the predetermined pressure. The piston 204 with moveablewithin the accumulator 200 to compress the gas in the spring chamber 208thereby prompting a spring force in opposition to the movement. In otherwords, the predetermined pressure in the spring chamber 208 exerts abias or a spring force against the piston 204 toward the collectingchamber 212.

With continued reference to FIG. 7, when the controller 196 controlsactuation to the lowered position (as shown), the control valve 184 ismoved to a first position and the pump provides high pressure hydraulicfluid to the first chambers 164, 164′ of the hydraulic cylinders 56, 60and the collecting chamber 212 of the accumulator 200. The high pressurehydraulic fluid exerts force on the plungers 160, 160′ and the rods 172,172′ are moved to the extended position so that the LSTA system 24 isarranged in the lowered position (i.e., the suspension/operationalmode). As the vehicle moves over uneven terrain, forces and movement maybe imparted to the LSTA system 24. The right hydraulic cylinder 56 andthe left hydraulic cylinder 60 are structured as suspension elements. Asa suspension force acts on the rods 172, 172′ hydraulic fluid is pushedfrom the first chambers 164, 164′ into the collection chamber 212 of theaccumulator 200 against the spring force of the spring chamber 208. Asthe piston 204 moves within the accumulator 200, the spring forceincreases and the piston 204 is forced toward the collecting chamber 212and the rods 172, 172′ are again extended. In this way, a spring/damper(i.e., spring damper) suspension system is provided by the samecylinders (e.g., the right hydraulic cylinder 56 and the left hydrauliccylinder 60) that are used for actuation between modes. The accumulator200 increases the reaction speed of the hydraulic system 64 when it isacting as a suspension system. The controller 196 controls the pump 180to maintain a constant pressure within the cylinders 56, 60 so that adesired ground force is maintained.

When the controller 196 controls actuation to the raised position, thecontrol valve 184 is moved to a second position so that high pressurehydraulic fluid is provided from the pump 180 to the second chambers168, 168′ of the hydraulic cylinders 56, 60 thereby retracting the rods172, 172′. In some embodiments, the return spring 188 biases the controlvalve to the second position so that the second position is the restposition. In some embodiments, the return spring 188 is arranged to biasthe control valve 184 toward the first position. In some embodiments,the control of the control valve 184 is arranged differently. Forexample, the control valve 184 may utilize pilots, more solenoids,manual controls, or other control architectures.

As shown in FIG. 8, when in the raised position, the spindles/knuckles128, 128′ are raised above the vehicle chassis 20. In the loweredposition, as shown in FIG. 12, the spindles/knuckles 128, 128′ arelowered below the vehicle chassis 20. FIG. 9 shows a rear view of theLSTA system 24, while FIGS. 10-13 show views corresponding to FIGS. 1-2and 8-9, respectively, but with the LSTA system 24 configured in thelowered position. The LSTA system discussed above provides anadvantageous auxiliary suspension for heavy vehicles that provides arequired ground clearance, and a fast-acting suspension system thatutilizing hydraulic cylinders acting as both actuators and suspensioncomponents. The parallelogram linkage provides side-to-side rigidity anda consistent kingpin caster angle during use. The steering or trackingsystem includes a centering feature and a connecting rod that isarranged in front of an axle frame and between linkage members toprovide a compact and protected architecture.

Although this description may discuss a specific order of method steps,the order of the steps may differ from what is outlined. Also, two ormore steps may be performed concurrently or with partial concurrence.Such variation will depend on the software and hardware systems chosenand on designer choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps.

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent, etc.) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” “between,” etc.) are merely used to describe theorientation of various elements in the figures. It should be noted thatthe orientation of various elements may differ according to otherexemplary embodiments, and that such variations are intended to beencompassed by the present disclosure.

It is important to note that the construction and arrangement of theload span tag axle as shown in the exemplary embodiments is illustrativeonly. Although only a few embodiments of the present disclosure havebeen described in detail, those skilled in the art who review thisdisclosure will readily appreciate that many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters, mountingarrangements, use of materials, colors, orientations, etc.) withoutmaterially departing from the novel teachings and advantages of thesubject matter recited. For example, elements shown as integrally formedmay be constructed of multiple parts or elements. It should be notedthat the elements and/or assemblies of the components described hereinmay be constructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present inventions.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the preferredand other exemplary embodiments without departing from scope of thepresent disclosure or from the spirit of the appended claims.

What is claimed is:
 1. A tag axle system comprising: an axle assembly; alinkage coupling the axle assembly to a vehicle chassis; and a hydrauliccylinder coupled between the vehicle chassis and the axle assembly, thehydraulic cylinder actuating the axle assembly between a raised positionand a lowered position, and acting as a spring damper suspensioncomponent.
 2. The tag axle system of claim 1, wherein the axle assemblyincludes a steering system, and wherein the steering system includes aconnecting rod coupled between a right wheel assembly and a left wheelassembly supported on the axle assembly.
 3. The tag axle system of claim2, wherein the connecting rod is positioned in front of an axle frame.4. The tag axle system of claim 1, wherein the axle assembly includes asteering system including a centering system that includes a springdamper.
 5. The tag axle system of claim 1, wherein the axle assemblyincludes a kingpin arranged at a kingpin caster angle, and wherein thekingpin caster angle is maintained in all loading conditions when theaxle assembly is in the lowered position.
 6. The tag axle system ofclaim 1, wherein the linkage includes a right upper link, a right lowerlink, a left upper link, and a left lower link, wherein the right upperlink and the left upper link are arranged at an upper link anglerelative to a central axis of the vehicle chassis, and the right lowerlink and the left lower link are arranged at a lower link angle relativeto the central axis, wherein the upper link angle is between about fivedegrees and about fifteen degrees, and wherein the lower link angle isbetween about five degrees and about fifteen degrees.
 7. The tag axlesystem of claim 6, wherein the upper link angle and the lower link angleare substantially the same.
 8. The tag axle system of claim 6, whereinthe upper link angle and the lower link angle are mirrored.
 9. The tagaxle system of claim 6, wherein there is about one-hundred-sixty-twodegrees between the upper link angle and the lower link angle.
 10. Thetag axle system of claim 1, wherein the linkage defines a parallelogramarrangement.
 11. The tag axle system of claim 1, wherein the hydrauliccylinder is a first hydraulic cylinder, and the tag axle system furthercomprising a second hydraulic cylinder.
 12. The tag axle system of claim1, wherein the hydraulic cylinder is a dual acting hydraulic cylinderdefining a first chamber and a second chamber, and the tag axle systemfurther comprising a hydraulic system that includes an accumulatorincluding a piston separating a pressurized spring chamber and acollecting chamber in communication with the first chamber of thehydraulic cylinder.
 13. The tag axle system of claim 12, wherein thehydraulic system further includes a control valve moveable between afirst position actuating the hydraulic cylinder to move the axleassembly to the raised position, and a second position actuating thehydraulic cylinder to move the axle assembly to the lowered position.14. The tag axle system of claim 1, the axle assembly further comprisingan axle beam, the axle beam further including: a plurality of plateswelded together, a plurality of axle brackets, and a plurality offasteners, wherein each one of the plurality of axle brackets is coupledto one of the plurality of plates using at least one of the plurality offasteners.
 15. The tag axle system of claim 14, wherein each one of theplurality of plates includes no more than two bends.
 16. The tag axlesystem of claim 1, wherein the linkage includes a right upper link, aright lower link, a left upper link, and a left lower link, wherein eachof the right upper link, the right lower link, the left upper link, andthe left lower link define a link bend between a midpoint of therespective link and the axle assembly.
 17. A tag axle system comprising:an axle assembly including an axle beam that includes a plurality ofplates welded together, each plate defining no more than two bends, anda plurality of axle brackets fastened to the axle beam; and a hydrauliccylinder coupled between a vehicle chassis and the axle assembly, thehydraulic cylinder actuating the axle assembly between a raised positionand a lowered position, and acting as a spring damper suspensioncomponent.
 18. The tag axle system of claim 17, further comprising: alinkage coupling the axle assembly to the vehicle chassis and includinga right upper link, a right lower link, a left upper link, and a leftlower link, wherein each of the right upper link, the right lower link,the left upper link, and the left lower link define a link bend.
 19. Thetag axle system of claim 17, wherein the axle assembly includes akingpin arranged at a kingpin caster angle, and wherein the kingpincaster angle is maintained in all loading conditions when the axleassembly is in a lowered position.
 20. A tag axle system comprising: anaxle beam including a plurality of plates welded together, each platedefining no more than two bends; a hydraulic cylinder coupled between avehicle chassis and the axle beam, the hydraulic cylinder actuating theaxle beam between a raised position and a lowered position, and actingas a spring damper suspension component; and a kingpin coupled to theaxle beam and arranged at a kingpin caster angle that is maintained inall loading conditions when the axle assembly is in the loweredposition.